Odd pits found in rod bearings of 160k mile minivan motor (photo)

[Lockasiam]

I had a thought regarding the pitting.
Could it be the pitting was caused by stresses and vibrations that were induced along the crankshaft during that time the vehicle was driven with one cylinder (the one I replaced the piston in due to no compression)?

I do not know how long the previous owner drove the vehicle like that. I do know I drove it home from the purchase point (200 miles) with cyl No 2 misfiring.

Maybe correcting the damaged piston and no compression problem would eliminate the originating source of the pitting I encountered?

View attachment 280206

If number 2 was the misfiring cylinder, why is #5 the one with the most pitting? I’m sure the misfiring could have something to do with the pitting but if #2 was the bad cylinder why does the direct opposite (functional) cylinder have the most damage?

 

[siriusc1024]

what viscosities are they comparing? Need a bit more than an abstract.

seems like we all need oil pan heaters, so we don't start the engine with cold oil, ever.

I'm simply pointing out that your refutation to my statement was incorrect.

I think the sharp edge has more to do with the cavitation.

But thicker oil is more likely to cavitate in this instance. May have contributed.

Since it's being rebuild I suspected thicker oil being used to bandaid a problem. Who knows maybe Lucas Oil Stabilizer was put in?

 

[Lockasiam]

Who knows maybe Lucas Oil Stabilizer was put in?

I never understood that stuff, just use a higher viscosity if you want the oil to be thicker

 

[MaximumMini]

If number 2 was the misfiring cylinder, why is #5 the one with the most pitting? I’m sure the misfiring could have something to do with the pitting but if #2 was the bad cylinder why does the direct opposite (functional) cylinder have the most damage?

As I understand it, it makes no difference the cylinder that malfunctions, it's the resonances and vibrations that are set up and travel across the crankshaft. The misfire could be on Cyl No1 and the majority of the damage could be at the opposite end of the crankshaft.

The cylinder that had no compression would actually transmit LESS linear forces onto that journal, so why would that journal bearing need to show the most damage?

 

[Lockasiam]

As I understand it, it makes no difference the cylinder that malfunctions, it's the resonances and vibrations that are set up and travel across the crankshaft. The misfire could be on Cyl No1 and the majority of the damage could be at the opposite end of the crankshaft.

The cylinder that had no compression would actually transmit LESS linear forces onto that journal, so why would that journal bearing need to show the most damage?

Makes sense

 

[Oliveoil2]

I learned that crankshafts must be ground in the direction of rotation...then polished in the opposite direction of rotation. Never knew that. Is that what you mean when you refer to Metallurgy?

No. I meant the rod bearings were incorrectly manufactured, and thus defective. They all developed almost exactly the same scar pattern. I’m not sure if having a chamfer on these original bearings would made any difference. It seems the composition of these original bearings might be the problem.

 

[MaximumMini]

No. I meant the rod bearings were incorrectly manufactured, and thus defective. They all developed almost exactly the same scar pattern. I’m not sure if having a chamfer on these original bearings would made any difference. It seems the composition of these original bearings might be the problem.

I wonder if that wear on the pictured bearings specifically is qualified as "Abnormal wear" being that the engine does have 160,000 miles on it?

 

[Lockasiam]

No. I meant the rod bearings were incorrectly manufactured, and thus defective. They all developed almost exactly the same scar pattern. I’m not sure if having a chamfer on these original bearings would made any difference. It seems the composition of these original bearings might be the problem.

Wonder if they changed anything to do with the bearings when they started recommending 5w20? I quit using 20 weight a while ago when I stopped getting oil for free and the engine seemed happier.

 

[Oliveoil2]

I wonder if that wear on the pictured bearings specifically is qualified as "Abnormal wear" being that the engine does have 160,000 miles on it?

I’d say they look odd, not abnormal given the mileage. But the good thing is you’ll never have to do them again!

 

[MaximumMini]

I’d say they look odd, not abnormal given the mileage. But the good thing is you’ll never have to do them again!

At least not for a long time. Took another 100 mile trip today and so far all seems good.

 

[ZeeOSix]

Meanwhile, I just used a jewelers loupe to examine the edges and they are not chamfered at all. Apparently a straight drilled hole.

The replacement rod bearings are chamfered.

I take it these where the bearing halves that were on the rod and not the rod cap. Where the new bearings Chrysler parts? Is so, sounds like the chamfered hole on the bearings was added for a reason.

Did the new bearings have a center groove or are they totally smooth like the originals?

 

[Exhaustgases]

The higher the viscosity the higher the load capacity.

 

[MaximumMini]

I take it these where the bearing halves that were on the rod and not the rod cap. Where the new bearings Chrysler parts? Is so, sounds like the chamfered hole on the bearings was added for a reason.

Did the new bearings have a center groove or are they totally smooth like the originals?

totally smooth. MAHLE brand

 

[MaximumMini]

Even though the Oil Pressure meets or slightly exceeds the Factory oil pressure specifications, it is on the lower end so I would like to bring the oil pressure up a bit. I'm considering replacing the oil pump and the oil pressure relief valve and spring.
From the precise measurements I took, I'm confident this is not an issue with excessive bearing wear.

It's a long shot but it could be a bit low due to deposits. The engine wasn't exactly clean inside but was also not worn.
It could benefit from several rounds of Valvoline RP

I would love to see 15-20 psi at idle (hot) and 30-40 psi at 1500 rpm. Is that unreasonable for an older, slow turning motor like the Chrysler 3.8L V6 circa 1999 ?

Anyone think that would (or would not) help?

 

[ZeeOSix]

totally smooth. MAHLE brand

Was the hole on the bearing half the one that went on the rod side (not in the rod cap)? If so, that hole is probably there to line-up with a hole in the rod which is typically used to squirt oil up under the piston - ie, an oil squinter built into the rod. If that's the case, then oil flows from the bearing clearance into that hole and through the hole in the rod. So the flow isn't coming into the bearing and into the bearing clearance. Do you recall the hole in the bearing lining up with a hole on the top side of the rod big end?

This will show what I'm talking about.

 

[MaximumMini]

Was the hole on the bearing half the one that went on the rod side (not in the rod cap)? If so, that hole is probably there to line-up with a hole in the rod which is typically used to squirt oil up under the piston - ie, an oil squinter built into the rod. If that's the case, then oil flows from the bearing clearance into that hole and through the hole in the rod. So the flow isn't coming into the bearing and into the bearing clearance. Do you recall the hole in the bearing lining up with a hole on the top side of the rod big end?

This will show what I'm talking about.

I follow you here.

The newly installed MAHLE bearings had the hole on BOTH halves. All 6 sets of two bearings had a hole in each half. You could not install them such that the oil hole did not line up.
As long as you put the tangs on both bearings on the same side (and there is only one way that will go) then you will have the hole lined up.

If there is still a way to get this wrong I will gladly open the bottom up again and recheck them all.
Thanks

 

[ZeeOSix]

I follow you here.

The newly installed MAHLE bearings had the hole on BOTH halves. All 6 sets of two bearings had a hole in each half. You could not install them such that the oil hole did not line up.
As long as you put the tangs on both bearings on the same side (and there is only one way that will go) then you will have the hole lined up.

If there is still a way to get this wrong I will gladly open the bottom up again and recheck them all.
Thanks

You're right, they can't be installed wrong because of the tang on the end of the bearing. Sounds like both haves were the same since there is no real functional purpose to have a hole in the bearing on the rod cap. MAHLE probably did it that way to ensue the oil squirter feed hole on the rod side wasn't covered up if only one half had the hole.

Did the original bearings also have a hole in both halves like the MAHLE bearings, or just one half?

So the failure you saw on the old bearings around the hole is most likely fatigue like some have mentioned. That area is in a pretty high pressure area of the supporting oil film wedge in bearing during the down stroke, so the idea is that high internal bearing pressure on the down stroke forces the most oil up through the squirter passage in the rod base.

 

[MaximumMini]

You're right, they can't be installed wrong because of the tang on the end of the bearing. Sounds like both haves were the same since there is no real functional purpose to have a hole in the bearing on the rod cap. MAHLE probably did it that way to ensue the oil squirter feed hole on the rod side wasn't covered up if only one half had the hole.

Did the original bearings also have a hole in both halves like the MAHLE bearings, or just one half?

So the failure you saw on the old bearings around the hole is most likely fatigue like some have mentioned. That area is in a pretty high pressure area of the supporting oil film wedge in bearing during the down stroke, so the idea is that high internal bearing pressure on the down stroke forces the most oil up through the squirter passage in the rod base.

The original bearings only had a hole in the one half of each bearing set per rod.

 

[Joba27n]

As I understand it, it makes no difference the cylinder that malfunctions, it's the resonances and vibrations that are set up and travel across the crankshaft. The misfire could be on Cyl No1 and the majority of the damage could be at the opposite end of the crankshaft.

The cylinder that had no compression would actually transmit LESS linear forces onto that journal, so why would that journal bearing need to show the most damage?

Worn out harmonic balancer/cheap aftermarket balancers/flywheels/torque converters also throw off engine harmonics and cause internal engine issues

 

[vssjim]

Clevite Clinic video from early sixties is an excellent training tool